Setup Description: Here is the long issue description to give you some background: I have a Ubuntu 11.04 host running QEMU emulator (qemu-system-x86_64. Qemu version 0.14.0)
The VM running on this host machine has an internal VM running a second Linux operating system. This is a VM inside a VM architecture, it being so for a reason.
Now, consider two such virtual machines running on this Ubuntu host.
Both these VMs talk to each other via bridged interfaces.
brctl show on Ubuntu host:
brctl show bridge name bridge id STP enabled interfaces base_br6 8000.12b225a87738 no btap_6_3
btap_6_7
The VMs running on this Ubuntu Host are: 1) VM_A
brctl show on VM_A bridge name bridge id STP enabled interfaces
base_br0 8000.001cae060703 no btap1 btap2 eth3 VM_A is also running QEMU emulator to host another VM ( alias internal guest or VM_A_Internal ) tipc-config -l -netid -addr -n issued on VM_A_Internal Links: broadcast link: up current network id: 7777
node address: <6.1.7> Neighbors: No nodes found.
eth0 on VM_A_Internal is configured as the bearer interface that sends out
TIPC neighbor discovery packets to detect its neighbor and locate VM_B_Internal as its neighbor.
Similar settings applicable to VM_B.
2) VM_B - running QEMU emulator to host VM_B_Internal
brctl show on VM_B bridge name bridge id STP enabled interfaces base_br0 8000.001cae060300 no btap1 btap2
eth3 tipc-config -l -netid -addr -n issued on VM_B_Internal Links: broadcast link: up current network id: 7777
node address: <6.1.3> Neighbors: No nodes found.
eth0 on VM_B_Internal is configured as the bearer interface that sends out TIPC neighbor discovery packets
to detect its neighbor and locate VM_A_Internal as its neighbor.
ISSUE: Now the issue is that all these packets ( TIPC control packets ) generated by the inner guest VMs are being dropped by the tap interfaces on VM_A and VM_B ( confirmed by the Rx drop count and Tx drop count shown by
netstat -i command) The host Ubuntu system also reports a drop of Rx & Tx packets at the base_br6 bridge.
How do we avoid the packet drops at the tap interfaces created by QEMU ? Am I missing something here ?
Note: The two inner guest VMs can see each other. Pinging the IP Addresses configured on the btap<x> interface works. However the neighborhood detection does not, indicating that these packets alone are being dropped. Firewall on the host
has been configured to FORWARD incoming and not REJECT/DROP any packet.
Appreciate any thoughts/inputs that will help me proceed further.